1. Field of the Invention
The present invention relates to a fluid dynamic bearing mechanism including a communicating channel, and a spindle motor, and a disk drive apparatus including the fluid dynamic bearing mechanism.
2. Description of the Related Art
Conventionally, hard disk apparatuses and optical disk apparatuses have spindle motors designed to rotate disks installed therein. Such spindle motors include a stationary portion, which is fixed to a housing of the apparatus, and a rotating portion, which is arranged to rotate while supporting the disks. The spindle motors are arranged to produce a torque through magnetic flux generated between the stationary and rotating portions, thereby rotating the rotating portion with respect to the stationary portion.
The stationary and rotating portions of the spindle motors are connected to each other through a bearing mechanism. In particular, a fluid dynamic bearing mechanism using a lubricating oil arranged between the stationary and rotating portions has often been used in spindle motors in recent years. JP-A 2001-65552, for example, describes an example of a dynamic pressure bearing apparatus arranged to rotate one of a shaft member and a sleeve relative to the other through a dynamic pressure action of the lubricating oil.
Generation of an air bubble in the lubricating oil in the fluid dynamic bearing mechanism may lead to a decreased accuracy of the rotation of the rotating portion. There is therefore a demand for a technique for reducing the generation of air bubbles in order to improve stability and reliability of the fluid dynamic bearing mechanism. Although a decrease in rotation performance caused by an air bubble generally falls within a permissible range in view of the quality required of conventional fluid dynamic bearing mechanisms, there is still a demand to reduce or eliminate the probability that any air bubble will be generated in the lubricating oil, in order to further increase the quality of fluid dynamic bearing mechanisms.